Urea-phosphoric acid cleaning composition



United States PatentO UREA-PHOSPHORIC ACID CLEANING 1 COMPOSITIONLawrence L. Little and Gilmore Chen, Morris Plains, N. J., assignors toE. F. Drew & Co., Inc., New York, N. Y., a corporationof Delaware NoDrawing. pplication October 1, 1952 Serial No. 312,654

11 Claims. (Cl. 252-436) The present invention is directed to detergentcompositions, more particularly to a composition including a strong acidand adapted for heavy duty cleaning of machinery. This application is acontinuation-in-part of co-pending application Serial No. 165,366, filedMay 31, 1950, and entitled Urea-Phosphoric Acid Cleaning Composition,now abandoned.

" In'cleaning machinery, particularly in food plants, it

has been customary to utilize compositions consisting of or containingsubstantial amounts of free phosphoric acid in the liquid state. Usuallysuch acid was concentrated. It served the purpose of cleaning suchmachinery or equipment to a fairly satisfactory result, although it isdesirable to have a more efiective composition for the purpose. It washighly disadvantageous in that the concentrated phosphoric acid wasinconvenient to handle and ship. It often occurred that some of thephosphoric acid was spilled on the floors of warehouses or of the plant,which caused destruction and corrosion of the floors and of the shoes ofthe workmen. It was also difficult to handle as it was corrosive to theclothing of the worker and to the skin. Furthermore, the phos} phoricacid was not fully efiective in the removal of protein deposits, mineralscale and grease. a It has also been proposed to provide a preparationintended to be used for Water softening purposes, which was the reactionproduct of phosphoric'acid and urea at high temperatures, up to 200 C.,to causedecomposition of the urea and the formation of ammonia, which inpart combined with the phosphoric acid to give ammonium phosphate whilesimultaneously dehydrating the product. This material was substantiallyneutral and did not have the necessary detergent properties for certainindustrial purposes,'such as in the cleaning of machinery and equip mentused in the .dairy industry. The product was not intended to be adetergent but only a water softening material. r e i The presentinvention is intended and adapted to overcome thedifficulties anddisadvantages inherent in prior compositions of the type described, itbeing among the objects of the present invention to provide an acidclean ing composition in which the corrosiveness is minimized,

which is easyto handle and ship and which is convenient to apply withoutdanger to the operator or his clothing.

It is also among the objectsof the present invention to provide acleaning composition which is eminently suitable for heavy dutycleaning, particularly for machinery in the food industries,particularly in equipment for pasteurizing milk and in vacuum pans forcondensing milk. i

- Itjisfurther among the objects of the present invention toprovide acleaning composition which is highly effective in removing deposits ofprotein and mineral matter and for removing oil, grease and wax' andalso to provide a strongly acid medium for the purpose.

tion containing about 85% of phosphoric acid. It is mixed with ureaor anaqueous solution thereof in the proportions of 1 part by weight of ureato 2 parts by weight of the phosphoric acid solution. A reaction occurswithout the application of heat forming a crystalline addition productwhich is easily handled and which is strongly acid. The solution may bewarmed to hasten the reaction but a temperature substantially above roomtemperatures is unnecessary, and in all cases it is below the boilingpoint of water to avoid decomposition.

To the reaction product is added a wetting agent selected from the classconsisting of cationic and non-ionic type of compounds. The amount ofwetting agent may vary considerable but it has been found that in mostcases at least 1% should be used, up to the maximum of 10%. Largeramounts are unnecessary as adequate wetting is obtained within thestated limits. The composition has a pH well under 4.7- and in thepreferred compositions the pH ranges from 2.0 to 3.0. Suitable cationicwetting agents are: Alkyl dimethyl benzyl ammonium chloride, alkyltrimethyl ammonium chloride, alkyl benzene trimethylammonium chloride,di-isobutyl phenoxy ethoxy ethyl dimethyl benzyl ammonium chloride, etc.Such compounds are described in the literature, as for example, inTaubet al. Patent No. 2,087,132, dated July 13, 1937. Non-ionic wettingagents suitable for this purpose include the polyglycol ethers and anyefiective non-ionic agent that has pronounced surface active properties.The glycol ethers are alkyl-aryl derivatives in which the alkyl radicalcontains from 6 to 22 carbon atoms. The glycol'contains hydrocarbonradicals having from 2 to 4 carbon atoms and the polyglycol containsfrom 10 to 100 glycol radicals. These polyglycol ethers are well-knownin the artas exemplified by the patent to Doutyet al. No. 2,396,776,dated March 19, 1946.

Additional substances may be introduced into the composition forproducing additional results. Such constituents include solid,crystalline or powdered acids, acid salts, or salts of polyvalentvmetals. The following are examples of substances which may be used:Boric or citric acid; monosodiuin phosphate, ammonium nitrate; calciumlactate, calcium acetate, magnesium lactate, aluminum nitrate orlactate. Such materials have a drying effect on the urea-phosphoric acidcrystals and make them more capable of absorbing liquid'wetting agents.Furthermore, they increase the solubilizing action on protein deposi s,and improve the emulsifying action against grease films. Such agents maybe used at the rate of from 550% of the total weight of the finishedproduct. i

The urea provides a solvent action on proteins, Whereas the phosphoricacid, is effective to dissolve mineral deposits and the combinationseems to have an additional eifect in that both protein andminerals areremoved much more efiectively by the composition than by the individualconstituentsused separately. It is believed that the effectiveness is;enhanced by the type of wetting agent added to the composition. Theacid compounds increase the ability of the composition to absorb thewetting agent and renderit more efiective. Also the acids and acid saltsact as butters to maintain the desired range of acidity. The alkaliearth metal salts and salts of aluminum have the effect of increasingthe ability of the composition to remove grease from the equipment andthey also act to preventthe formation of lumps of the urea-phosphoricacid reaction product.

In the use of the composition, it is dissolved in water to form asolution containing about 2 to 5% of the composition. It is applied atelevated temperatures, usually above 60 C., to the equipment to becleaned, and if desired a scrubbing action may be used. When thecleaning operation is completed, the spent solution is removedand theequipment is rinsed with hot water to Example 1 The followingcomposition is provided:

48% phosphoric acid 85 24% urea 24% boric acid 4%polyglycol ether Theurea is dissolved in the phosphoric acid, causing a reaction to takeplace which raises the temperature of the solution. The; mixture :isallowed to cool with stirring, wherebya powder is formed. The boric acidis uniformly mixed into the product, rendering the same more freelyflowable. The liquid wettin'g agent is then added and stirred intothepowder.

Example 2 The following composition is provided:

48% phosphoric'acid (85%) 24% urea 22% calcium lactate 6% alkyl benzenetrimethyl ammonium chloride Example 3 The following composition isprovided:

48% phosphoric acid (85%) 24% urea boric acid 14% aluminum nitrate 4%alkyl dirnethyl benzyl ammonium chloride The phosphoric acid solution ismixed with the wetting agent, and the urea added to produce the reactionproduct with the phosphoric acid. Separately a mixture is made of thewetting agent, boric acid and aluminum nitrate. Then the two mixturesare stirred together until a homogeneous composition is obtained.

Example 4 The following composition is provided:

% phosphoric acid (85 20% urea 20% citric acid 15% calcium acetate 5%polyglycol ether The urea and the phosphoric acid are mixed and thereaction allowed to go to completion. Then the remaining constituentsare mixed together and they are stirred into the urea-phosphoric acidreaction product.

Example 5 A comparative test was made with the product of the presentinvention an'd a product of the prior art, wherein. phosphoric acid andurea were heated up to a tempera- 4 ture of 220 C. for several hours.The following table indicates the results obtained by the test:

Cleaning Product Time,

Product A was the prior art urea phosphoric acid decomposition product,and product B was applicants product. Both of the products were usedunder identical conditions for the purpose of cleaning dried andhardened milk residues. They were placed in solution in water and thetreatment of the articles being cleaned was at a temperature of 130 F.The present product gave complete cleaning in a very short time, whereasthe product of the prior art required about four times the time ofcleaning as applicants product.

Example 6 Comparative tests were made between the products described inExample 5, for the purpose of removing grease from metal articlesincluding equipment used in the dairy industry. The products weredissolved in water and the cleaning operation was conducted at 130 F.The followin table shows the results obtained by the comparative tests:

Solution Strength Product Cleaning Time A Over3 hours. A Over 3 hours. B79 minutes.

B 36 minutes.

It will be noted that even with a large quantity of the prior artproduct, the time of cleaning remained overthree hours. On the otherhand, with applicants product, the larger amounts required less time andin all cases the time required for cleaning with the present productswas a fraction of that necessary with the prior art.

, The present composition overcomes the disadvantages of the liquidphosphoric acid in that it may be handled readily and safely in all itsphases including shipment, storage and use. The composition isconsiderably more effective in dissolving protein deposits, greasesoils, and mineral deposits. cidal agent is used as wetting agent, theproduct is a potent germicide and combines detergent and germicideaction into one product and operation.

Although the invention has been described setting forth several specificembodiments thereof, the invention is not limited thereto as variouschanges in the details may be made within the spirit of the invention.For instance, the ratio of urea to phosphoric acid may be .variedsomewhat and within narrow limits and it has been found that suchvariation may be as much as 10% more or less urea than called for by thel to 2 ratio. It is not necessary to use concentrated phosphoric acidbut the ratio of the urea thereto should remain the same. The reactionproduct may be formed in aque-' one solution and such solution may beeither concentrated or dilute. One may even start with a water solutionof urea. In all such modifications, the urea-phosphoric acid ratio ofobut 1:2 by weight is based upon 85% phosphoric acid in water solution.However, it is usually preferred to work with concentrated solutions ofphosphoric acid and solid urea because the final. product is a powderwhich may be readily and economically shipped.

The solid crystalline acids and acid salts, named herein,

and of acid salts, such as mono-phosphates and mono- When a quaternaryammonium germi-.

sulphates, which are applicable. The wetting agents need not be solids,but liquid wetting agents, such as diisobutyl phenoxy ethoxy ethyldimethyl benzyl ammonium chloride, may be used.

These and other changes in the details of the invention may be madewithout departing from the principles herein set forth and the inventionis, therefore, to be broadly construed and not to be limited except bythe character of the claims appended hereto.

I claim:

1. An acid cleaning composition comprising a mixture of the crystallineaddition product of urea and phosphoric acid, said product having a pHbelow 4.7, the ratio of urea to concentrated phosphoric acid by weightbeing about 1 to 2, with a wetting agent taken from the class consistingof quaternary ammonium cationic wetting agents and polyglycol ethernon-ionic wetting agents having to 100 glycol radicals.

2. An acid cleaning composition comprising a mixture of the crystallineaddition product of urea and phosphoric acid, said product having a pHbelow 4.7, the ratio of urea to concentrated phosphoric acid by weightbeing about 1 to 2, with a wetting agent taken from the class consistingof quaternary ammonium cationic wetting agents and polyglycol ethernon-ionic wetting agents having 10 to 100 glycol radicals, the amount ofwetting agent being less than 10% of said addition product.

3. An acid cleaning composition comprising a mixture of the crystallineaddition product of urea and phosphoric acid, said product having a pHbelow 4.7, the ratio of urea to concentrated phosphoric acid by weightbeing about 1 to 2, with a wetting agent taken from the class consistingof quaternary ammonium cationic wetting agents and polyglycol ethernon-ionic wetting agents having 10 to 100 glycol radicals, the amount ofwetting agent being less than 10% of said addition product, saidcomposition containing at least 5% of a solid free acid.

4. An acid cleaning composition comprising a mixture of crystallineaddition product of urea and phosphoric acid, said product having a pHbelow 4.7, the ratio of urea to concentrated phosphoric acid by weightbeing about 1 to 2, with a wetting agent taken from the class consistingof quaternary ammonium cationic wetting agents and polyglycol ethernon-ionic wetting agents having 10 to 100 glycol radicals, the amount ofwetting agent being less than 10% of said addition product, saidcomposition containing at least 5% of a substance taken from the classconsisting of citric acid, an acid salt and boric acid.

5. An acid cleaning composition comprising a mixture of the crystallineaddition product of urea and phosphoric acid, said product having a pHof about 2.0 to 3.0, the ratio of urea to concentrated phosphoric acidby weight being about 1 to 2, with a wetting agent taken from the classconsisting of quaternary ammonium cationic wetting agents and polyglycolether non-ionic wetting agents having 10 to 100 glycol radicals.

6. An acid cleaning composition comprising a mixture of the solidaddition product of urea and concentrated phosphoric acid having a pHbelow 4.7 and obtained by mixing said urea and phosphoric acid with aquaternary ammonium cationic wetting agent having wetting properties,the amount of wetting agent being less than said reaction product, theratio of urea to phosphoric acid in said product being about 1 to 2 'byweight.

7. An acid cleaning composition comprising a mixture of the solidaddition product of urea. and concentrated phosphoric acid having a pHbelow 4.7 and obtained by mixing said urea and phosphoric acid with awetting agent taken from the class consisting of quaternary ammoniumcationic wetting agents and polyglycol ether non-ionic wetting agents,said wetting agents being alkyl-aryl compounds, the amount of wettingagent being less than said reaction product, the ratio of urea tophosphoric acid in said product being about 1 to 2 by weight, andcontaining at least 5% of citric acid.

8. An acid cleaning composition comprising a mixture of the solidaddition product of urea and concentrated phosphoric acid having a pHbelow 4.7 and obtained by mixing said urea and phosphoric acid with awetting agent taken from the class consisting of quaternary ammoniumcationic wetting agents and polyglycol ether non-ionic wetting agents,said wetting agents being alkyl-aryl compounds, the amount of wettingagent being less than said reaction product, the ratio of urea tophosphoric acid in said product being about 1 to 2 by weight, andcontaining at least 5% of an acid salt.

9. An acid cleaning composition comprising a mixture of the solidaddition product of urea and concentrated phosphoric acid having a pHbelow 4.7 and obtained 'by mixing said urea and phosphoric acid with awetting agent taken from the class consisting of quaternary ammoniumcationic wetting agents and polyglycol ether non-ionic wetting agents,said wetting agents being alkylaryl compounds, the amount of wettingagent being less than said reaction product, the ratio of urea tophosphoric acid in said product being about 1 to 2 by weight, andcontaining at least 5% of ammonium nitrate.

10. An acid cleaning composition comprising a mixture of the solidaddition product of urea and concentrated phosphoric acid having a pHbelow 4.7 and obtained by mixing said urea and phosphoric acid with awetting agent taken from the class consisting of quaternary ammoniumcationic wetting agents and polyglycol ether non-ionic wetting agents,said. wetting agents being alkyl-aryl compounds, the amount of wettingagent being less than said reaction product, the ratio of urea tophosphoric acid in said product being about 1 to 2 by weight, andcontaining at least 5% of sodium phosphate.

11. An acid cleaning composition comprising a mixture of the solidaddition product of urea and concentrated phosphoric acid having a pHbelow 4.7 and obtained by mixing said urea and phosphoric acid with awetting agent taken from the class consisting of quaternary ammoniumcationic wetting agents and polyglycol ether non-ionic wetting agents,said Wetting agents being alkyl-aryl compounds, the amount of wettingagent being less than said reaction product, the ratio of urea tophosphoric acid in said product being about 1 t0 2 by weight, andcontaining at least 5% of a salt of a metal taken from the classconsisting of the alkali earth metals and aluminum.

References Cited in the file of this patent UNITED STATES PATENTS2,338,987 Watzel Jan. 11, 1944 2,396,776 Douty et al Mar. 19, 19462,558,167 Beghin et a1. June 26, 1951 2,593,259 Brissey et a1. Apr. 15,1952

1. AN ACID CLEANING COMPOSITION COMPRISING A MIXTURE OF THE CRYSTALINEADDITION PRODUCT OF UREA AND PHOSPHORIC ACID, SAID PRODUCT HAVING A PHBELOW 4,7, THE RATIO OF UREA TO CONCENTRATED PHOSPHORIC ACID BY WEIGHTBEING ABOUT 1 TO 2, WITH A WETTING AGENT TAKEN FROM THE CLASS CONSISTINGOF QUATENARY AMMONIUM CATIONIC WETTING AGENTS AND POLYGLYCOL ETHERNON-IONIC WETTING AGENTS HAVING 10 TO 100 GLYCOL RADICALS.